Field of the Invention
The present invention relates to a technique for combining a plurality of continuously captured images.
Description of the Related Art
In conventional imaging apparatuses such as cameras, the photographable field angle is limited by the characteristics of the shooting lens. To shoot images in a wide range, it is necessary to sacrifice resolution. In addition, the aspect ratio of acquirable images is also limited by hardware.
There is a conventional technique of panoramic composition to address the foregoing problems. In the panoramic composition, a plurality of images with overlapped regions is combined to generate a large image. Using this method makes it possible to acquire a wider image beyond the characteristics of the lens. In addition, combining the plurality of images makes it possible to change the aspect ratio.
To acquire a composite image without strangeness by the panoramic composition described above, the alignment of the images on the imaging apparatus is essential. Japanese Patent Laid-Open No. 2004-134993 proposes a method by which to perform the alignment using motion vectors. According to this method, the motion vectors are detected using the feature amounts obtained from contrasts, luminance components, or color difference components of different images to be combined.
The larger the sizes of captured images are, the larger the load of vector calculation to be used for the alignment of the images to be combined becomes. Japanese Patent Laid-Open No. 2009-27437 discloses determining the motion vectors not from the entire images but from only the partial regions of the images.
However, when the partial regions set for obtaining the motion vectors are from feature-less images, the high-accuracy detection of the motion vectors is difficult, and it can be impossible to provide favorable panoramic composition.